21123131221998 has 72 divisors (see below), whose sum is σ = 49559823992952. Its totient is φ = 6499200936384.

The previous prime is 21123131221991. The next prime is 21123131221999. The reversal of 21123131221998 is 89912213132112.

21123131221998 is a `hidden beast` number, since 2 + 1 + 1 + 2 + 31 + 312 + 219 + 98 = 666.

It is a super-2 number, since 2×21123131221998² (a number of 27 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123131221991) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 102634665 + ... + 102840267.

It is an arithmetic number, because the mean of its divisors is an integer number (688330888791).

Almost surely, 2^{21123131221998} is an apocalyptic number.

21123131221998 is an abundant number, since it is smaller than the sum of its proper divisors (28436692770954).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21123131221998 is a wasteful number, since it uses less digits than its factorization.

21123131221998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 239410 (or 239394 counting only the distinct ones).

The product of its digits is 93312, while the sum is 45.

The spelling of 21123131221998 in words is "twenty-one trillion, one hundred twenty-three billion, one hundred thirty-one million, two hundred twenty-one thousand, nine hundred ninety-eight".